A Guide to the Muscles in the Back and Shoulders

If your intent is to increase the size of your shoulders and back, it is important to first understand their anatomy. By knowing where they are located and what they do, each of them can be targeted with specific exercises. There are three major muscles groups in the shoulders and back including:

Deltoid

The deltoid is the main muscle of the shoulder and is comprised of three distinct fiber groups called bands – the anterior, lateral and posterior. On the lower end, all three bands terminate on the humerus in the upper arm. However on the upper end, each band has its own connection point: the anterior at the collarbone (clavicle); the lateral at the acromion (tip of the clavicle just above the shoulder joint; the posterior at the scapula (shoulder blade).

The deltoid controls almost all movement of the arm moving in the shoulder joint – front, back and out to the side.

Trapezius

This complex muscle group occupies most of the upper back and runs from the back of the neck and extends out to the top of the shoulders and then narrows as it continues down the back finally terminating midway down the spinal column. Its purpose is two-fold: to stabilize the shoulder blades in addition to allowing them to move and rotate; to extend the head at the neck.

Rhomboid

The rhomboid is actually two separate muscles stacked one on top of the other. On the bottom is the rhomboid major, on top is the rhomboid minor. Both the minor and major connect the shoulder blade to the spine.

Latissimus Dorsi

Running from the humerus down the back and wrapping midline around the sides, it attaches at to the pelvic girdle at the lower end to the pelvis and to spinal column from midway down to the bottom. It mainly functions to pull your extended arm back to its normal retracted position, as in swimming or rowing a boat.

Erector Spinea

The erector spinea is a series of eight different muscles that run up and down the spine. They radiate out from the spine and connect at various places. Many terminate up and down the rib cage to hold that anatomy structure in alignment with the spine.

When viewed from the back, there isn’t anything more impressive than a fully developed back. While there are many more exercise to define precise areas, these will start the development process of each major muscle group in the back and shoulders.